Heating-furnace



W. C. BUELLl Jn. HEATING FURNACE. APPLIcATloN man "n.21, ma.

1 344,436 Patented June 22, 1920.

3 SHEETS-SHEET l.

WITNESSES INVENTOH @Wm am W. C. BUELL, 1R. HEATING FURNACE.

APPLICATIDN FxLEn ma. 21. |918.

1 ,344,436. Patented June 22, 1920.

3 SHEETS-SHEET 2.

f I "l/111111 WITNESSES www@ W. C. BUELL, JR.

HEATING FURNACE. APPLICATION FILED MAII.2I, I9Ia.

Patented June 22, 1920.

3 SHEETS-SHEET 3.

WJTNESSES INVENTQR UNITED STATES PATENT OFFICE.

WILLIAM C. BUELL, JR., 0F PITTSBURGH, PENNSYLVANIA,` ASSIGNOR TO TATE- JONES & CO., INC., 0F PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA.

Specication of Letters Patent.

HEATING-FURNACE.

Patented J une 22, 1920.

To nl] whomy it may concern.'

Be it known that I, IVILLIAM C. BUELL, Jr., a resident of Pittsburgh, Allegheny county, Pennsylvania, have invented a new and useful Improvement in Heating-Furnaces. of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specification, in which- Figure 1 is a transverse vertical section of one form of heating furnace having my invention applied thereto;

Fig. 2 is a vertical section of a portion of the furnace showing an additional feature of the invention;

Fig. 3 is a detail horizontal section through the vertical flue; and

Fig. 4 is a side elevation of a portion of the furnace equipped with a number of flues and of the character shown in Fig. Q.

My invention has relation to improve ments in heating furnaces. and more par# ticularly to furnaces using a plurality of burners in multiple in connection with a multiple arrangement of npdraft flues.

In the accompanying drawings, I have shown my invention as aiplied to a well known type of overfired furnace and will describe the invention in connection with a furnace of this type, without, however, limiting it in any way thereto.

In furnaces of this type as heretofore constructed, the multiple lues at each side of the furnace have been placed within the side walls of the furnace, and in order to provide for these flues it has been necessary to make these walls of greater thickness than would otherwise be the case. Thus, in order to provide for such lues, a minimum thickness of at least thirteen and a half inches has been required, and as the fines are made of standard brick dimensions, they are. therefore, four and a half inches wide, leaving four and one-half inches of brick between the heating chamber and lues and four and one-half inches between the ues and insulating material. There heavier firebrick walls are used, the additional thickness is usually placed between the flue and the insulating material. For instance, with an eighteen-inch wall. the usual division outward from the heating chamber is four and one-half inches of irebrick; four and one-half inches of Hue,

and nine inches of firebrick at the outer side of the flue.

The overfired furnace is a type of furnace adapted to produce uniform, accurate and controllable temperatures for the heat-treating of alloy steels and the like. The temperature re uired for the work seldom exceeds 1800Q and is generally lower than 1600o F. Experience has shown that with a heating chamber temperature of 2000o F., a nine inch thickness of refractory wall backed up on the outside by from two and one-half to four and one-half inches of insulating material is ample to prevent an unduly high heat transfer and loss of heat through the side walls. The weight supported by these side walls is relatively insignificant, and thickness of walls is not a yfactor of strenoth. Under these conditions, the necessity of walls having a thickness in excess of nine inches is due entirely to the incorporation of the fines in the side walls.

One object of my invention relates to the elimination of the flues from the side walls, whereby there is effected a saving of at least one-third of the material entering into the side walls, together with the contingent reduction in labor cost. This latter is still further reduced, inasmuch as there is provided a wall which is all straight brick laying and does not require the special skill and time required when the flues are built into the wall.

A further object of my invention relates to the fuel economy to be secured by the removal of the fiues from the side Walls. At the point where the gases enter the Hues at the floor or hearth of the furnace, they become waste gases, having done all their useful work, and the flues are merely a medium to convey the gases to the top of the furnace, which is a convenient point to vent them into the atmosphere. A stack to carry ofl" the waste gases or to produce a downward draft through the heating chamber is unnecessary in furnaces of this t pe and is seldom used. Repeated tests whlch I have made show that the temperature of the gases on leaving the fiues is considerably higher than the temperature at the point where they leave the heating chamber. This shows that the gases have taken up heat in passing upward through the flues, which is, of course, a condition of unnecessary waste.

This is due to the fact that in order to produce a temperature in the heating chamber of 1600o F., it is frequently necessary to produce a temperature above 2000o F. in

. the upper or combustion chamber. As there is customarily about four and one-half inches of refractory material between the combustion chamber and the flues, it follows that the wall at the combustion chamber side of the flues becomes highly heated. I have observed temperatures of approximately 1500" F. at this point. The flue gases passing this point at a temperature several hundred degrees lower rapidly absorb heat, and in order to maintain temperature equilibrium through the brick, the flow of heat at this point 1s comparatively high. Actual tests made by me show that the flues within the side walls actually draw off from the furnace in excess of ten per cent. of the total heat of the furnace. By eliminatin these ilues, I thereby prevent a very consi erable fuel waste. Y

A still further object of my invention has relation to the utilization of the temperature of the waste gases. I have found that in the case of overfired furnaces, these gases frequently leave the heating chamber at a temperature of approximately 1500O F., and

generally in the neighborhood of 1200o F l after the furnace chamber has reached its normal temperature. Assuming the fuel oil to be the fuel employed and perfect combustion, the gases leaving the heating chamber and entering the flues at 1200o F will contain 45,800 B. T. U.s of sensible heat for each gallon of fuel burned, or approximately 31.7 per cent.

My invention provides simple means whereby a part of the sensible heat of these gases may be utilized to heat the air required to support combustion.

Referring first to that form of my invention shown in Fig. 1,`the numeral 2 designates the heating chamber of the furnace; 3 the side walls, and 4 the combustion chamber above the perforated interior arch 5. 6 designates flues which lead outwardly at oposite sides of the chamber 2 at its base.

hese flues are for the waste gases, and a plurality of them is arranged along each side of the furnace. It is usual to provide burners distributed in a horizontal plane along the length of the furnace, these being placed at six foot oi' even shorter centers on each side, so that there is a burner to every three feet of furnace length. One or more of the lues 6 is provided for each burner in order to produce uniformity of draft, temperature, etc.

In accordance with my invention, each of the flues 6 extends horizontally outward through the side walls and through the base extensions 7 of such walls. where they enter the vertical flues 8, which are placed wholly externally of the side walls. These flues 8 may be of any suitable character, either metal or brickwork. By thus locating the flues, I accomplish the two first stated objects of my invention in a simple and effective manner.

In Figs. 2, 3 and 4, I have shown the additional feature whereby portions of the sensible heat of the waste gases may be utilized in a simple manner to reheat the air required to support combustion in the furnace. In these figures, the corresponding parts are given the same reference numerals as in Fig. l, with the letter a affixed thereto. The construction is similar to that shown in Fig. 1, except that each of the flues 8a is inclosed by an outer surrounding flue 9. Each of these flues 9 at its lower end communicates with a chamber 10, supported on the base extension 7a. At its upper end, it opens into an air inlet chamber 11, into which air may be supplied through the connection 12. This'air may come from any suitable source and under any desired degree of pressure. In Fig. 2, I have shown an air supply pipe 13, which is common to a plurality of the flues and is, in turn, supplied by a main 14.

It will be readily seen that the arrangement shown in these figures constitutes a countercurrent recuperative device. The waste gases enter the recuperator at the bottom, passing upwardly through the flues 8", and giving up their heat to the air flowing down in the flue formed by the other casing 9. The cold air meets the flue gases at their coldest point, while the air leaves the recuperator in contact with the flue gases at the hottest point by application of the true countercurrent principle.

The chamber 10 has an outlet connection 15, by which air may be taken by any suitable system of piping to the furnace burner and pipes 16.

The diameter of the inner and outer flue members can be varied at will, and their length may be modified to meet any conditions that may arise. The entire construction is of marked simplicity and relative cheapness.

I claim:

1. A heating furnace having a plurality of waste gas iues leading outwardly from its lower portion along each side thereof, said flues extending horizontally through the side Walls of the chamber and communieating at their outer ends with upwardly extending flues which are exterior to said side walls, substantially as described.

2. A heating furnace having its heating chamber provided with a waste gas flue extending horizontally outward through the lower portion of its side wall, a vertical flue communicating with the horizontal flue, said vertical flue being exterior to the side wall,

and a chamber surrounding the vertical flue for preheating the air supply to the furnace, substantially as described.

3. A heating furnace having itsy heating chamber provided with a waste gas outlet flue extending horizontally outward through rthe lower portion of its side w'all and then l the lower portion of its side wall, and a countercurrent recuperative device connected with such flue, said countercurrent device being located exteriorly to the side wall, substantially as described.

5. A heating furnace having its heating chamber provided with a waste gas outlet flue extending horizontally outward through the lower portion of its side wall, and a countercurrent recuperative device connected with such flue, said recuperative device comprising an inner flue through Vwhich the waste gases pass upwardly and an outer surrounding flue through which air is adapted to be forced downwardly, substantially as described.

6. A heating furnace having its heating chamber provided with a plurality of waste gas outlet Hues arran edaat the lower portion of each side thereogf, said fiues extendin outwardly through the side walls of sai chamber, and yan air-recuperating device connectedto the outlet of each of said lues, substantially as described.

7. A heating furnace havin its heating chamber provided with a plura it of waste gas outlet lues arranged at the lbwer portion of each side thereof, said lues extending outwardly through the side walls of said chamber, and a counter-current air-recuperating device connected to the outlet of each of said flues, substantially as described.

8. A heating furnace having an upper combustion chamber and a lower heating chamber, said furnace having a waste gas flue leading outwardly from said heating chamber through the side walls of the furnace, and a verticall terior of said side wal s and communicatin at its lower end with the outer end of sai waste gas flue; substantially as described.

9. A heating furnace having an upper combustion chamber and a lower heating chamber, said furnace having -a plurality of waste gas flues leading outwardly from the o posite sides of said heating chamber tlirough the side walls of the furnace, and vertically extending flues ad'acent to and exterior of said side walls an communicating at their lower ends with the outer ends of said waste gas fines; substantially as described. f

10. A heating furnace having an upper combustion chamber and a lower heating chamber, said furnace having a waste as flue leading outwardly from said heating chamber through the side walls thereof, a vertically extending lue exterior of and ad jacent to said side walls and communicating at its lower end with the outer end of said waste as flue', and a counter-current recuperatlve device co eratin with said vertical flue; substantia ly as escribed.

In testimony whereof I have hereunto set my hand.

WILLIAM c. BUELL, JR.

extending flue ex- Certificate of Correction.

It is hereby certified that in Letten Patent No. 1,344,436, granted June 22, 1920, upon the application of William C. Buell, jr.. of Pittsburgh, Pennsylvania, for an lmpljovement in Hentin Izrnaces, an error appears in the printed specification correction asfo lows: Page 3, after line 78 insert the following as claims 1I; A' heating furnace having a heating chamber and means for introducing a heating medium at the 'loper portion of said chamber, said furnace having a waste ya# 12W leading Oum' fg from said heating cham-ber through the side 'walls of the fume, a 'vertically extending #ue exterior of said side walls and communi j its lower end with the outer end of said waste gas flue,y substantially as 12. A heating furnace having a hcating chamber and means for introducing znoducte of combination into the ujpeyortion of said chamber, said chamber hommg a luralicy of waste gas ues ma outwardly through the lower ortz'on of, the 'walls of P said heating chamber, and vertically extending flue@ adjacent to and exterior of said side walls and communicating al their lower ends with thc outer ends of said 'waste gas fines, substantially as described.

and that thesaid Letters Patent should be read with this corx'ction therein that the same may conform to the record of the case in th Patent Omoo.

Signed and sealed this 2d day of.June, A. D. 1925.

KARL FENNING,

Acting Commissioner of Patents. 

